Acute aortic dissection is the most common fatal condition that involves the aorta; nevertheless, despite major advances in noninvasive diagnosis, the correct antemortem diagnosis is made in less than half the cases. To promote continued improvement in the prompt recognition of aortic dissection, we present a review of the Mayo Clinic experience with 235 patients who had 236 substantiated aortic dissections. At the time of initial assessment, 158 patients (67%) had acute and 78 patients (33%) had chronic aortic dissection. Hypertension was the most common predisposing factor (78% of patients overall). The acute onset of severe chest pain was the most common initial complaint (74%), but 33 patients (15%) had painless aortic dissection and abnormal chest roentgenographic findings. Less common manifestations included congestive heart failure, syncope, cerebrovascular accident, shock, paraplegia, and lower extremity ischemia. The initial clinical impression was aortic dissection in 62% of patients overall. In 17 patients (28%), the correct diagnosis was not made before postmortem examination. Although the clinical features of aortic dissection have gained wider appreciation, the diagnosis still remains unsuspected in a substantial number of patients. In a patient who has a catastrophic illness and unexplained symptoms that could be of vascular origin, especially in the presence of chest pain, aortic dissection should always be included in the differential diagnosis.